1.  'BODMAS' Rule:
  This rule depicts the correct sequence in which the operations are to be executed, so as to find out the value of given expression.
  Here B - Bracket,
O - of,
D - Division,
M - Multiplication,
A - Addition and
S - Subtraction
  Thus, in simplifying an expression, first of all the brackets must be removed, strictly in the order (), {} and ||.
  After removing the brackets, we must use the following operations strictly in the order:
  (i) of (ii) Division (iii) Multiplication (iv) Addition (v) Subtraction.
2.  Modulus of a Real Number:
Modulus of a real number a is defined as
|a| =  
a, if a > 0
-a, if a < 0
Thus, |5| = 5 and |-5| = -(-5) = 5.
3.  Virnaculum (or Bar):
  When an expression contains Virnaculum, before applying the 'BODMAS' rule, we simplify the expression under the Virnaculum.